1. Field of the Invention
The invention is generally related to the area of audio technologies. In particular, the invention is related to controlling of audio amplifiers in devices based upon data traffic detection.
2. The Background of Related Art
Automatic power shutdown is an important feature in many electrical appliances. One of the appliances commonly seen is a stereo system that includes a powered subwoofer. The subwoofer is automatically shutdown when the stereo system is powered off or produces no sound (e.g., in CD mode with no CD is played). On the other end, the subwoofer is automatically tuned on when the stereo system is powered on, thus eliminating the need of turning on or off two devices manually or sequentially. Another example is an uninterruptible power supply (UPS) supporting a computer system. The UPS provides power in an event that regular power to the computer system is suddenly off. As an automated preventative measure, the computer system is configured to shut down itself when the UPS is running on a low battery level or beyond a predetermined time so as to avoid corrupting files, or damaging other parts in the computer system.
The implementation of the automatic power shutdown feature is largely based upon special circuitry or analog control circuits to detect a signal level against a predetermined level. In the stereo system example, if audio signals to the subwoofer are not detected or substantially lower than a fixed level for a period of time, the subwoofer is sent a signal to be powered off. Likewise, when audio signals to the subwoofer are detected, the subwoofer is sent a signal to be powered on. In the UPS example, the detection mechanism is similar. The battery in the UPS is constantly or periodically measured against a predetermined level or the operation time thereof is measured. When either one of the measurements is below a certain level, the computer system receives a signal or an instruction that triggers the automatic shutdown process.
The analog solution of automatic power shutdown is not effective when used in a distributed system comprising multiple devices that need to automatically shut down while not in use. For example, a plurality of networked audio devices each of which has or associated with one or more power amplifiers share audio sources. The detection of an analog signal to one of the audio devices on a data network would be difficult and ineffective. Additional hardware (i.e., circuitry), if needed, would increase the cost and complexity of such system. There is, therefore, a need for solutions of automatic shutdown suitable for such system without adding extra hardware.